In order to explore possible etiologic differences between tubal infertility in women who had been physician-diagnosed as having pelvic inflammatory disease ("overt" PID) and in women who had not ("silent" pelvic inflammatory disease), we made use of self-reported data from a large, population-based, case-control study of infertility in King County, Washington. Responses from 33 infertile women with no history of physician-reported PID and 129 infertile women with such a history were compared to those of 501 fertile women. No cultures or blood for antibody titers were obtained. Logistic regression was used to compute the relative risks for silent and overt PID-related tubal dysfunction associated with various lifestyle and contraceptive habits in an effort to identify practices that potentially affect these outcomes. In general, practices associated with an increased risk of overt tubal disease, such as use of Dalkon Shield and other types of intrauterine devices, were also associated with an increased risk of silent tubal disease, but to a lesser extent. Women who used oral contraceptives for longer than three years had a decreased risk for silent disease (relative risk = 0.5, 95% confidence interval = 0.3-0.8), but their risk for overt disease did not decrease to the same extent (relative risk = 0.9, 95% confidence interval = 0.3-2.5). These results suggest that silent and overt tubal disease share many common lifestyle risk factors.